The present invention relates to a heat-sealing apparatus and, more particularly, to such a heat-sealing apparatus, which draws air out of the packing bag when sealing it.
In order to keep food fresh, a polymeric packing bag may be used to seal food, and a vacuum pump may be used to draw air out of the packing bag when sealing it. Because the top and bottom side edges of the mouth of a polymeric packing bag are normally closely attached to each other, it takes much time to open the mouth and to keep the mouth open when drawing air out of the packing bag. U.S. Pat. No. Re,34,929 discloses a packing bag 1 for use with a vacuum pump 12. The packing bag 1 has intersected ribs 11 on the inner surface around the mouth. Because of the presence of the intersected ribs 11, the mouth of the packing bag 1 can easily be opened. However, the manufacturing cost of this particularly designed packing bag 1 is high.
It is the main object of the present invention present invention to provide a heat-sealing apparatus, which draws air out of the packing bag when sealing it. According to one aspect of the present invention, the bottom shell of the heat sealing apparatus has a top center recess, and a packing bag stretcher supported on a compression spring in the top center recess and adapted to stretch open the mouth of the loaded packing bag for enabling a vacuum pump to draw air out of the loaded packing bag when sealing it. According to another aspect of the present invention, the packing bag stretcher comprises a bearing plate supported on the compression spring, a press plate suspending above the bearing plate for pressing the bottom side edge of the mouth of the loaded packing bag on the bearing plate, two L-shaped clamping plates disposed at two sides of the bearing plate and adapted to clamp the mouth of the loaded packing bag on the press plate, and two torsional springs respectively connected between two sides of the gearing plate and the two L-shaped clamping plates. According to still another aspect of the present invention, the bearing plate has a transversely extended air hole connected to the vacuum pump in the bottom shell by a suction tube for enabling the vacuum pump to draw air out of the loaded packing bag.